During his time in China, Jack Bauer was tortured by men working for Cheng Zhi in order to uncover whether Hong Wai or Li was working with the Americans as an undercover agent in the Chinese government. Despite harsh treatment such as whippings and electric shocks, Jack did not speak a word after being shown pictures of both men. Wu San warned Cheng that the repeated torture would kill Jack, so Cheng eventually tried an alternative route: a ruse in which Jack believed he was extracted by twomen claiming to be American rescuers. With a nod of his head, Jack then unintentionally betrayed Hong Wai, and Cheng was satisfied that the informant had been killed. ("Season 6 Prequel")